95 
middle, abruptly curved towards the sides, and regularly arched from the beaks to the front. 
Beak extended beyond that of the dorsal valve and much incurved. Dorsal valve nearly flat 
or slightly convex above, with a wide undefined sinus, which often extends in front across the 
entire width of the shell. Surface smooth, or with obscure concentric lines of growth ; shell- 
structure finely punctate. 
Length from two to four or five lines, the width being equal to the length or a little 
less. : 
Detached valves of C. glans-fageu are of not uncommon occurrence in the Corniferous 
Limestone. Occasionally individual examples are found having a length of from six to eight 
lines, and these Mr. Billings thinks may perhaps be distinct. I am inclined to think, however, 
that they are only large and tumid specimens of C. glans-fagea. : 
Locality and Formation.—Corniferous Limestone of Port Colborne. 
116. CENTRONELLA HECATE (Billings). 
Centronella Hecate (Billings), Canadian Journal, New Series, Vol. VI., p. 272, Fig. 99. 
Shell small, “ elongate, oval, or sub-rhomboidal ; apical angle from 45° to 60°; sides some- 
what straight from the beak to about the middle, where, making a rounded angle, they con- 
verge towards the front margin, which is somewhat truncate for about one-third the width. 
Ventral valve strongly but broadly carinate from the beak along the middle to the front, 
descending with a flat or gently convex slope to the sides ; in outline only, gently arched longi- 
tudinally ; in some specimens nearly straight ; the beak small, elongated, erect, and with a trian- 
gular foramen. Dorsal valve gently convex in the upper half, and with a wide shallow sinus in 
the lower half. Surface smooth. Length from two to four lines; width about three-fourths 
the length” (Billings). 
Our collections comprise a few specimens which appear to agree in their essential cha- 
racters with the above descriptions ; but the materials at present in my hands are simply 
sufficient for identification. 
Locality and Formation.—Corniferous Limestone, Port Colborne. 
CHAPTER, LY. - 
POLYZOA OF THE CORNIFEROUS AND HAMILTON FORMATIONS, 
The remains of Polyzoa in the Devonian Rocks of Western Ontario are very abundant, 
and they are of unusual interest in many ways. Unfortunately, however, they are, for the 
most part, more or less fragmentary, and their study is thus attended with special difficulty, 
since there is no class of organisms requiring greater skill and patience in their interpretation. 
Altogether, I have been able to identify nineteen species of Polyzoa, of which no, less than 
fifteen appear to be new, whilst several forms have come to light belonging apparently to new 
generic types. There remains, however, a considerable number of forms, of which the ma- 
terials at present in my hands are too fragmentary to justify me in describing them definitely, 
The forms which I have considered myself warranted in describing, belong to the following 
genera :—Fenestella (five species), Ieetepora (two species), Polypora (four species), Cryptopora 
(one species), Carinopora (one species), Twniopora (two species), Ceriopora [7] (one species), 
Botryllopora (one species), Clathropora (one species), and Ptilodictya (one species). The 
genera Fenestella, Itetepora, and Polypora are typical members of the family of the Fenestellide, 
and they comprise more than half of the total number of species identified. It is to these 
three genera, also, that most of the undeterminable fragments belong ; so that the Fencstellide 
must be considered as having had a very great development in the Devonian period in North 
America. The genera Cryptopora and Carinopora, now characterised for the first time, also 
belong to the Fenestellide, though they exhibit many extraordinary, and indeed, altogether 
unprecedented, points of structure. The new genus Botryllopora can hardly be compared 
with any known group of the Paleozoic Polyzoa, but the well-known Silurian genus Ptilodic- 
tya is represented by at least one form ; and Ceriopora (?) Hamiltonensis is related to certain 
well-known types in both the Silurian and the Carboniferous Rocks. 
